He adds that the find also represents "the first time a specific nuclear gene [has been] retrieved from Neanderthals".

Krause and his colleagues extracted DNA from two 38,000-year-old Neanderthals collected from El Sidron Cave in Asturias, Spain.

To avoid contamination with human DNA, the researchers took extraordinary precautions, such as wearing masks, lab coats and sterile gloves, as well as freezing the Neanderthal bodies before transporting them out of Spain.

The Neanderthals appear to have been cannnibalised after their death, which may have helped preserve their DNA over the millennia.

"The de-fleshing might [have] minimised the decay of the bones and their endogenous DNA," Krause says.

Doing the split

Before this study, scientists thought that modern humans evolved the special language version of the gene after we split from Neanderthals more than 300,000 years ago.

Before that time, we shared a common ancestor, perhaps the big-brained Homo heidelbergensis or Heidelberg Man.

Now it's unclear when the language-linked gene arose, since Heidelberg Man may have first emerged around 600,000 years ago.

But Krause says "it would be more plausible" if the changes to the gene arose just before humans and Neanderthals split "around 350,000 years ago, and not much before".

Interbreeding and language

Researchers continue to debate whether or not modern humans and Neanderthals interbred.

If they did, that could explain the shared gene and the propensity for speech. But studies on that question remain inconclusive.

Krause says he and his team have found "no hard evidence" of interbreeding, but "the Neanderthal genome sequence will ultimately solve this question".

In it, Trinkaus says there is no "silver bullet" like language, "which identifies us as 'human' and which can be used to identify past human forms as more or less 'human'."

"[The findings] not only permit the much maligned Neanderthals a degree of human behaviour that has been evident in their burials and archaeological record for 100 years, they also permit a perspective on the emergence of modern human behaviour, including language."

The study, he suggests, may not only change our view of Neanderthals, but also of ourselves.